Start by grabbing the nearest build sites and putting Lumber Mills on them before starting your headquarters. Concentrate on Forges, then build up the perimeter defenses and one or two towers near the northwest because you will be using your camp against the initial Rohirrim rushes. After several rushes, the AI will have no more but will probably have upgraded archers into Elven Warriors.

Secure the north and west flanks with Saruman and a small elite force. Save the main force and reinforcements from your Uruk Pit to secure the middle passage where the bulk of the enemy will come.
On the side passages, ignore the enemy if small (peasant) forces take out your Lumber Mills because they can't get past your main base perimeter defenses. Instead, fight to the base sites and build defensive towers to block (most) further incursions.
Now, be careful with your veteran units (if you want to preserve them -- they can go up to level 4 in this map) and push into the main camp. If you need respite, the northwestern base (if you built it with defenses) can give you temporary haven against archers until you eventually whittle down the Rohan forces with infantry.
When you finally push into the camp, destroy the Archery Range first, which leaves only farms and peasant rabble as enemy units. Destroy their command center in the middle, then leave the area and set up blocking units to take out peasant sorties -- but do not win the map yet.

The small valley with ents and a building site is typically passive unless your forces or Saruman gets too close (usually by passing its north end), so you can safely save that for last.